It would seem sexual plasticity, or at least its potential, may not be uncommon in fish.

True, fish are fairly plastic organisms, even in terms of sex. But as your quote said it often "determined by a combination of internal and external signals." Estrogen mimics seem like pretty good signals to me.

First of all, the "scientist" in this article cites concentrations of DDT in sediment.

Further contributing to feminization, the chemical fertilizer DDT acts like estrogen, he said. The chemical was dumped into waters by industry decades ago, Kelley said. DDT has since been banned, but it persists in the environment, he said.

DDT breaks down rapidly in salt water into DDE. For him to cite DDT to the media is pure grant mongering. Then you go on:

Estrogen mimics seem like pretty good signals to me.

A characteristically extended inference not supported by quantitative data. To back such an assertion, you would have to show the differences in the effects of estrogens from treatment plants versus "estrogen mimics" from agricultural chemical residues in hornyhead turbot (which I guarantee you has not been done), never mind distinguishing them from any natural propensity toward protogyny in that species (which very likely also has not been done given that I haven't found a single study). Further, the data from your link contributes some rather interesting facts.

Several agencies in Southern California measure the bioaccumulation of trace metals and chlorinated hydrocarbons in muscle tissue of hornyhead turbot as part of their receiving water monitoring programs. In 1991 off Orange County, p,p-DDE averaged 362 µg/kg wet weight in hornyhead turbot liver and 5 µg/kg dry weight in the sediments (CSDOC 1992). In the same year in Santa Monica Bay, p,p-DDE averaged 7.8 mg/kg wet weight in liver and 81 µg/kg dry weight in the sediments (City of Los Angeles 1992). The highest tissue levels of chlorinated hydrocarbons in hornyhead turbot occur on the Palos Verdes Shelf; concentrations decline to the north and south (Mearns et al. 1991).

First of all, the paper (correctly) cites quantitative amounts of DDE, a breakdown product of DDT in saltwater. DDT breaks down in saltwater so rapidly that for the article to state that it was present and persistent in marine sediments is pure farce.

Second, the bioaccumulated fish liver concentrations of DDE (which extensive research has been shown not to be a mutagen) in Orange County are below 1 ppb! To assert that concentrations that small are capable of inducing sex change would require serious experimental proof.

Third, according to the linked article, in Santa Monica Bay the bioaccumulated concentrations in fish liver are 7.8ppm, or nearly 8,000 times that of Orange County even though the concentrations in sediments are only 18 times higher (demonstrating considerable capacity to store the and filter out the chemical (it would be really interesting to assay the quantity of such chemicals in other tissues of the respective samples)). So, if the numbers of male fish displaying protogyny and the degree of progression are the same in Orange County versus Santa Monica Bay, chances are that the DDE isn't the culprit.

Then there's this little gem:

It's likely that Southern California waters contain naturally-produced estrogen as well as synthetic estrogen contained in birth control pills, he (Kelly) said.

No mention is made in either the article above nor the linked article of the absolute concentrations of marine estrogens, nor whether they are unusual for the Pacific Coast, nor is any mention made in the article above of even an estimate of the percentage contribution of estrogens in the water from anthropogenic sources from birth control pills versus natural background concentrations.

Now that is scary!

No, the really scary thing is that the article doesn't mention that protogyny in fish is not unusual.

For you to go off implying in dark tones that some sort of pending crisis exists, when protogyny in fish is so common, when the article is full of errors directly attributable to the "scientist," when the concentrations of bioaccumulated DDE vary wildly with no mention of any difference in consequences, and with no quantitative data of either the total quantity of estrogens, much less the anthropogenic fraction, now THAT is scary.

29 posted on 11/29/2005 9:34:12 AM PST by Carry_Okie
(The environment is too complex and too important to manage by central planning.)